The present invention relates to a hose with corrugated metal tube, which is suitable for fuel conveying hose for automobiles, refrigerant conveying hose or any other fluid conveying hose, and more particularly to a hose connecting structure for connecting a hose with corrugated metal tube to a mating pipe.
Typical rubber hoses, for example, made of blended product of acrylonitrile-butadiene rubber and polyvinyl chloride (NBR/PVC blend) which is excellent in resistance to gasoline permeability, have been used for conveying fuel for automobiles or the like in view of their high vibration-absorbability, easy assembling or the like. However, for the purpose of global environment protection, the regulations have been recently tighten against permeation of fuel for automobiles or the like, and are anticipated to be further tighten in the future. Further, hoses are demanded to meet toe requirements to convey highly permeable fluid such as hydrogen gas used in fuel cells or carbon dioxide (CO2) refrigerant.
Then it is anticipated difficult to satisfy the future requirements with hoses made only of organic materials such as rubber or resin.
Accordingly, it is currently considered to adapt a hose with a corrugated metal tube as an inner layer because the hose with corrugated metal tube is expected to have an extremely high fluid impermeability to meet the demand for a fluid impermeable hose.
As for a hose with corrugated metal tube, such hoses as disclosed in the following Document 1, Document 2 and Document 3 are known.
Document 1 JP, A, 2001-182872
Document 2 US20020007860A1
Document 3 J?, U, 51-150511
In case of the hose with corrugated metal tube, even if adapted for hydrogen gas of small molecular mass used for fuel cells, a corrugated metal tube in or as an inner layer reduces gas permeation zero, i.e., completely eliminates permeation of gas.
However, as an inner layer, i.e., a corrugated metal tube in the hose with corrugated metal tube is difficult to deform, if the hose with corrugated metal tube is adapted, it will be a problem how to construct fastening or connecting structure on an end portion of the hose with corrugated metal tube so as to assure sealing property thereon.
Up to now, as shown in FIG. 6, a hose connecting structure for an end portion of a typical rubber hose is usually constructed as in following manner. First, a rigid metal inert pipe or connecting pipe 200 is inserted in a hose body 202, a socket fitting 204 including an inwardly directed collar-like portion 206 is fitted onto the hose body 202. And then, the socket fitting 204 or a sleeve thereof is securely compressed or swaged radially inwardly to the hose body 202. Thereby the hose body 202 along with the socket fitting 204 securely fastened to the connecting pipe 200 with one another and a seal is provided on an end portion of the hose.
However, in case of a hose with a corrugated metal tube in or as an inner layer, sufficient close-contact relation is hardly obtained between the corrugated metal tube and the connecting pipe or the connecting part. If there is a scratch on a surface of the corrugated metal tube in a compressed or swaged range, internal fluid easily leaks out of that scratch.
Therefore, in such a hose with corrugated metal tube, a tip end of the corrugated metal tube is bonded to the connecting pipe or connecting part by welding to assure sealing property therebetween.
However, a great deal of difficulties is presented in welding operation for sealing an end portion of the hose. It not only raises production cost of a hose, but also lowers mechanical strength of the connecting pipe 200 or the corrugated metal tube due to affection by heat during welding and thereby will be a factor to damage quality assurance of the hose.
In case that welding is adapted for bonding and sealing in a hose including a corrugated metal tube, if the corrugated metal tube is vibrated, bent, or is internally subject to pressure, a stress is repeatedly concentrated in a weld-bonded area between an end portion of the connecting pipe 200 and the corrugated metal tube. The connecting pipe 200 is rigid and inflexible while the corrugated metal tube is flexible, and there is a problem that the weld-bonded area or the corrugated metal tube is likely broken.
Once the corrugated metal tube or the weld-bonded area is broken in that way, a hose with corrugated metal tube looses a gas barrier property. In some cases, properties of the hose such as flexibility and vibration absorbability are deteriorated and the hose will be unusable.
The above are described with reference to a hose for conveying hydrogen gas used in a fuel cell as example. The similar problems are anticipated in common to any hoses. For example, it may be the case that a hose with corrugated metal tube is employed for conveying fuel gasoline for the purpose to deal with gasoline or the like permeating to an air or for high temperature and high pressure application due to high output power of equipment where low permeation is severely regulated. Or it may be the case that a hose with corrugated metal tube is employed to convey carbon dioxide (CO2) as refrigerant fluid, which is low in amount of particles just like hydrogen and has high gas permeation. Further, it may be any other case that a hose with corrugated metal tube is applied in fields under severe regulations against gas permeation.
It is an object of the present invention to provide a hose connecting structure for a hose with corrugated metal tube to settle the problems described above.